Otoreflectance (OR) is a new class of hearing-test instruments utilizing acoustic signals presented and recorded in the ear canal. OR instruments address the following limitations in existing instruments to screen and diagnose middle-ear function: (1) detection of otitis media, (2) prediction of conductive hearing loss, (3) detection of middle-ear dysfunction in infants receiving a newborn hearing screening exam or follow-up audiologic assessment, and (4) general use to assess middle-ear function at frequencies in the bandwidth of speech. An OR test provides measurements over a wideband range (approximately 0.25 to 8 kHz) of such transfer functions as reflectance and admittance, and power absorbed by the ear canal and middle ear. Energy reflectance and absorbed power are OR functions that are relatively insensitive to probe position in the ear canal, and thus are well suited to interpreting middle-ear function at higher frequencies. One type of OR instrument can be used with probes similar to otoacoustic emission probes to screen middle-ear function in several seconds at ambient ear-canal pressure. Phase I of this project established the feasibility of measuring such OR responses in normal-hearing adults and children, as well as in children with surgically confirmed middle-ear fluid. Phase I also implemented a wideband OR test to assess the function of the middle-ear muscle reflex, and compared reflex thresholds in infants and adults with thresholds measured using conventional instruments. In Phase II, a wideband OR tympanometry instrument will be implemented, adding a pump to vary ear-canal static pressure, and OR tympanometry norms will be measured in adults. The test performance of ambient-pressure OR and conventional 226-Hz tympanometry will be compared in young children to detect middle-ear fluid and to predict a conductive hearing loss associated with otitis media with effusion. OR tympanometry will form part of a new objective and efficient wideband test to measure middle-ear muscle reflex thresholds, which will be compared to thresholds in adults and infants measured using a conventional test. The test performance of the ability of OR tympanometry, ambient-pressure OR, and conventional 1000-Hz tympanometry to detect middle-ear dysfunction will be compared in infants also receiving a standard newborn hearing screening exam. Outcomes from Phase II will evaluate whether OR is more accurate than conventional tests to screen and diagnose middle-ear dysfunction in clinical applications of important societal concern. [unreadable] [unreadable]